Originally Posted by NewEdgeStang00

Hmm TRUEBLU its very interesting how incorrect fluid can cause such a racket! I will definitely ask the guys tomorrow. My car goes back to the shop in the morning

Originally Posted by CaptainRon

from a stop turn your steering wheel sharply to the left or right all the way then go ahead and take off and note if theres any clicking or grinding noises from the rear.
jack the rear up and spin the wheels and try to hear for anything abnormal.

and finally what I would do is to bounce the rear of the car several times while its in park real good and see if you hear anything, this way you can try to narrow it down to the cause.

Originally Posted by NewEdgeStang00

Syracuse, sorry unfortunately that's not the noise I'm hearing. It's more like a crunching noise like metal against the brake rotors.

Originally Posted by TRUEBLUE3934

Probably NOT the same issue for you, but my AuburnPro diff began making a TERRIBLE clunking/grinding noise and sounded like it was going to come apart at any moment when maneuvering at lower speeds. It turns out that the fluid I was using was WRONG!

I had installed Royal Purple Synthetic 140-85(I think). I spoke with an engineer at Auburn, the diff was designed to run a non-synthetic 80/90 fluid plus Ford Friction Modifier. I drained/flushed the Royal Purple and put the basic 80/90 dino oil in and the noise went completely away. I was shocked!!!

I share this just to make a point that the diff was designed around a certain fluid and using something else could cause terrible results. Note: my noise did not begin immediately either. It took a couple of weeks for the noise arise.

GOOD LUCK figuring this issue out!

Originally Posted by 69MustangCoupe393cid

I have a horrible noise from my rear while turning. I've had Amsoil Synthetic in mine for about 25k miles and had the noise for about 10k.



EXACTLY the noise I have.



I put in 75-140?? I think Amsoil without the modifier. Seemed fine for about 15k miles.




Reason for saying everything above... I have an appointment to get my rear completely rebuilt Friday. I'll be doing most of it. I'll also be using that same fluid and if I have any problems I'm going to point to the fluid. Someone PM me in a week or 2 if I forget to post up my findings. Hopefully what I find will help someone else out.

Originally Posted by NewEdgeStang00

My car goes in tomorrow morning so I will post what I find out. The Royal purple gear I got came with the kit I bought from American Muscle. It's a 4.10 ford racing gear so is that OK or should I be using something else??

Originally Posted by NewEdgeStang00

so I'm sitting in the lobby and of course things always turn out this way - can't make the noise come up again. And I guarantee once I take it back out it'll make it again after a few minutes.. Well the guys initial diagnosis was that it may be the front wheel bearing. But I've heard all kinds of problems with the wheel bearings and I'm sure it's not it, because it only happens the split second before stopping or making a 90 degree right turn

Originally Posted by Syracuse315

Having just gone through this last week, the best way to test for a bad bearing is when the car is on the lift. Grab the top and bottom of the tire, and see if it will rock back and forth. If it does, you should do both bearings because they fail almost simultaneously.